Aspects of the present invention relate to debris barriers. More specifically, aspects of the present invention relate to debris barriers for audio transducers. In particular this invention relates to barrier membranes useful for preventing a variety of solid, liquid, and vapor contaminants from modifidying or damaging the performance of the acoustic transducers, while at the same time providing essentially an acoustically transparent passage of sound. Applications include the protection of small microphones and receivers (speakers for example) commonly used in applications including hearing aids, hearing protection, communications equipment, personal entertainment devices and performance sound monitoring equipment.
Hearing device technology has progressed rapidly in recent years. First generation hearing devices were primarily of the Behind-The-Ear (BTE) type, where an externally mounted device was connected by an acoustic tube to a molded shell placed within the ear. With the advancement of component miniaturization, modern hearing devices are focusing primarily on one of several forms of In-The-Ear or ITE devices. Three main types of ITE devices are routinely offered by audiologists and hearing instrument specialists. Full shell ITE devices rest primarily in the concha of the ear and have the disadvantages of being fairly conspicuous to a bystander and relatively bulky to wear. Smaller ITE devices fit further in the ear canal and are commonly referred to as In-The-Canal (alternatively referred to as “ITC”) devices. Such hearing aids fit partially in the concha and partially in the ear canal and are less visible but still leave a substantial portion of the hearing device exposed. Recently, Completely-In-The-Canal (alternatively referred to as “CIC”) hearing devices have come into greater use. As the name implicates, these devices fit in the ear canal and are essentially hidden from view from the outside.
In addition to the obvious cosmetic advantages these types of transducers or in-the-canal devices provide, they also have several performance advantages that larger, externally mounted devices do not offer. Placing the hearing device deep within the ear canal and proximate to the tympanic membrane (ear drum) improves the frequency response of the device, reduces distortion due to jaw extrusion, reduces the occurrence of the occlusion effect and improves overall sound fidelity.
One common problem associated with the microphones and recievers used in these and other electroacostic devices used in and around the human ear is the infusion of debris of various forms, causing the transducers to perform poorly and in some cases fail to function. Perhaps the most common forms of debris are referred to as Cerumen or ear wax, which is noted to appear in solid, liquid and vapor forms. It has long been a desire to develop sufficient barriers for such debris that are transparent to sound, durable, and easy to clean. In addition to ear wax, other forms of debris such as sweat, water, and hair spray for example often cause similar problems.
Numerous devices have been developed in an effort to solve such problems. Such devices generally include passive and active mechanical solutions that impede the flow of debris, providing a means to capture some portion of the accumulated debris.
Known passive and active mechanical solutions impede the flow of debris, providing a means to capture some portion of the accumulated debris and provide a direct path for desired sounds to pass through the barrier. Examples of such known solutions include U.S. Pat. No. 4,553,627 to Gastmeier et al.; U.S. Pat. No. 4,953,215 to Hans-Joachim Weiss et al.; U.S. Pat. No. 5,278,360 to Carbe, and U.S. Pat. Nos. 6,105,713; and 6,349,790 to Brimhall et al, each of which are incorporated herein by reference in their entirety. Such devices are adapted to trap solid and semi-solid debris while letting liquid and vapor forms pass through. Such devices are often difficult to clean due to small openings or passages in their design. In addition it is often difficult to determine that these disclosed devices are filled with debris.
Some known disposable, passive mechanical solutions use open cell foam type materials to capture debris, while allowing desireable sound to pass through. Examples of such known disposable passive mechanical solutions include, for example, U.S. Pat. Nos. 5,401,920 and 5,920,636 to Oliveira et al. The disclosed devices are disposable, not cleanable and may capture solid and liquid debris but would have difficulty capturing vapor debris.
It is also known that passive devices may make use of semi-rigid microporous membranes (Microporous PTFE for example) adapted to trap debris and enable some sound to pass. Examples of such membranes include U.S. patent application No. 2002/0177883 to Tziviskos et al; U.S. Pat. No. 6,505,076 to Tziviskos et al; U.S. Pat. No. 6,512,834 to Banter et al; U.S. Pat. No. 6,134,333 to Flagler; U.S. Pat. No. 5,828,012 to Repollé et al; U.S. Pat. No. 4,987,597 to Haertl; and U.S. Pat. No. 4,071,040 to Moriarty, each of which is incorporated herein by reference in their entity. These devices appear to be effective for some applications but are known to limit the frequency response of the corresponding transducer due to their relatively high acoustic impedance. These devices are generally limited to speech bandwidth transmission, and will eventualy plug up due to solid and liquid debris accumulations, hence requiring replacement. Due to the porosity of such devices, debris in the form of vapor are allowed to pass through.
Other known passive devices place a non-porous membrane between an acoustic transducer and the offending source of debris, where the non-porous membrane tends to act as a barrier to all forms of debris, and to varying degrees let sound effectively pass through. Early examples of such barriers are described in U.S. Patent No. 3,169,171 to Wachs et al. and U.S. Patent No. 4,424,419 to Chaput each of which are incorporated herein by reference in their entirety. Such barriers are generally used in speech bandwidth applications, restricted in performance between about 10 Hz to about 4 kHz. The Wachs patent discloses a cap (or protective barrier) which is made of flexible thin paper, or plastic material such as sheet vinyl, polyethylene or the like. No details are provided as to the acctual acoustical performance of this device, but it appears to have restricted frequency range. In the Chaput patent, the described membrane is fabricated from 10 μm Mylar on to which Aluminum had been vacuum deposited.
In U.S. Patent No. 5,748,743 to Weeks, incorporated herein by reference in its entirety, describes a two piece hearing aid, one piece of which provides a barrier to ear wax using an integral membrane that is described to be “as thin as possible in order to minimize attenuation of the amplified sound from the micro speaker in the hearing aid device to the user's ear drum. Weeks indicates that the membrane must be less than 0.010″ thick and ideal performance occurs with membranes below 0.001″ thick.” However, the Weeks Patent does not disclose important information regarding membrane characteristics, such as membrane dimensions, membrane physical and chemical properties, and resulting barrier performance characteristics.
U.S. Pat. No. 6,164,409 to Berger detailed mechanical specifications for a membrane used with hearing aids. However, the Berger patent does not provide sufficient measurement data to demonstrate performance in two particular areas: low and high frequency response; distortion and attenuation properties of the device. The Berger Patent only discloses frequency response data between 400 and 4 kHz, which primarily covers the speech communications range. The suitability of the performance of the described device is questionable from the vantage point of acceptable acoustical attenuation. In addition, various embodiments of the device disclosed by Berger feature “a rigid, non-porous, non-sound permeable vibratable membrane”. It should be appreciated that the disclosed membrane structure has a high density, thickness and stiffness making it to rigid to move effectively for use with small transducers used in ear applications. Such membranes will result in unacceptable attenuation and distortion of sound passage for these types of applications. Furthermore, the disclosed membrane has a diameter between about 0.375″ to about 0.20″ (about 9.53 mm to about 5.09 mm) which would appear to have little practical value in hearing aid applications due to large size.
Other known attempts to provide non-porous barriers used with hearing aids have failed due to distortion or barrier deterorization. For example, a barrier introduced Knowles Electronics in 1994 called the “WaxShield” became unusable when exposed to oils in the ear, as well as demonstrating unacceptable distortion. In addition, similar devices from major hearing aid devices such as Siemens and Phonak were never introduced into production apparently due to distortion and/or frequency response problems when fabricated with dimensions suitable for hearing aid applications.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.